A spot on your shoulder that has always been there may be completely harmless. A dark mark that appeared recently, changed over a few months or simply looks unlike your other moles deserves closer attention. When comparing melanoma versus harmless mole, the safest rule is not to diagnose it in the mirror. Notice what is new or changing, then arrange a professional skin check.

Australia’s high UV levels make this a practical health decision, not a cosmetic concern. Melanoma can grow quickly and may spread if it is not found early. When detected and treated early, outcomes are often very good. Every minute counts when a suspicious lesion needs assessment.

What is a harmless mole?

A common mole, also called a naevus, is a cluster of pigment-producing cells. Many Australians have moles, and most are benign. They can be flat or raised, tan, brown, pink or close to skin-coloured. Some are present from childhood, while others develop through early adulthood.

Harmless moles tend to remain stable. They usually have a relatively even colour, a defined edge and a shape that looks balanced from one side to the other. That does not mean every benign mole looks perfectly round or identical. Bodies are varied, and some harmless moles are irregular-looking. Stability over time is reassuring, but it is not a guarantee.

Moles can also change for non-cancerous reasons. Hormonal changes, including pregnancy, can make existing moles appear darker or larger. Friction from clothing may irritate a raised mole. Even so, do not assume a change is harmless because there is an explanation that seems plausible. A clinician can assess the spot with a dermatoscope and decide whether monitoring, photography or removal is appropriate.

Melanoma versus harmless mole: the differences that matter

Melanoma is a cancer of melanocytes, the cells that give skin its pigment. It can begin in an existing mole, but many melanomas arise as a new spot on previously normal skin. It does not always look dark brown or black. Melanoma can be pink, red, purple, skin-coloured or without pigment, which is why a changing lump or sore should not be dismissed because it lacks the classic appearance.

The ABCDE guide can help you remember features that warrant a skin check:

• A – Asymmetry: one half does not match the other.
• B – Border: the edge is blurred, notched, scalloped or uneven.
• C – Colour: there are multiple shades, or the colour is unusual for you.
• D – Diameter: it is larger than about 6 mm, although melanomas can be smaller.
• E – Evolving: it is changing in size, shape, colour, surface or sensation.

Of these, evolving is often the most useful warning sign. A mole that becomes darker, develops an uneven edge, starts bleeding, crusts repeatedly or feels itchy, tender or painful should be assessed. A spot that looks different from your other moles is also worth acting on. This is sometimes called the ugly duckling sign: it may not meet every ABCDE feature, but it stands out from the pattern of spots on your own skin.

A harmless mole is generally predictable. Melanoma is more likely to be new, changing or distinctly different. But visual rules are screening tools, not a diagnosis. Some melanomas can appear small and neat; some benign moles can look unusual. Only a trained clinician, and sometimes a biopsy examined in a laboratory, can tell the difference with certainty.

Check the places you cannot easily see

Melanoma can occur anywhere there are melanocytes. It is common on the back in men and on the legs in women, but it can develop on the scalp, ears, buttocks, soles of the feet, between the toes and beneath nails. Ask a partner, family member or trusted friend to look at your back and scalp, or use mirrors in good light.

Do not overlook the nail unit. A new or widening brown or black band in a nail, especially if pigment spreads onto the nearby skin, needs prompt medical review. So does a persistent dark spot on a palm, sole or inside the mouth. These sites are especially relevant for people with skin of colour, who can develop melanoma despite having a lower overall risk from UV exposure than people with very fair skin.

If a spot is bleeding after being caught on clothing, that may be simple trauma. If it bleeds without a clear reason, fails to heal, or keeps recurring in the same place, book an appointment. The same applies to a sore that persists for more than a few weeks.

Who should be especially alert?

Anyone can develop melanoma, but risk is higher for people with fair skin, freckles, light eyes or hair, a history of blistering sunburn, frequent sun exposure or past use of solariums. Australia has banned commercial solariums, yet previous exposure remains relevant.

You should also be more proactive if you have many moles, atypical moles, a personal history of melanoma or other skin cancer, or a close family history of melanoma. Outdoor workers, gardeners, surfers, fishers, tradies and people who spend long periods driving or exercising outside may receive substantial cumulative UV exposure. UV damage can occur on cloudy days, and it is not limited to summer.

Risk factors help determine how regularly you should have skin checks, but they should never be used to rule melanoma out. A person without an obvious risk factor can still notice a suspicious lesion. Likewise, younger adults can develop melanoma, so a changing mole should not be put down to age.

What happens at a skin check?

A skin check is usually straightforward. The clinician asks about the lesion, your personal and family history, and any changes you have noticed. They examine your skin, often using a dermatoscope, a handheld instrument that magnifies structures beneath the skin surface.

Depending on what they find, they may reassure you, photograph a lesion for comparison, arrange short-term monitoring, or recommend a biopsy or excision. If melanoma is diagnosed, treatment commonly begins with surgery to remove the cancer and a margin of surrounding skin. The next steps depend on the melanoma’s thickness, type and whether there is any evidence it has spread.

Do not try to remove, freeze or treat a suspicious mole yourself. Home remedies and over-the-counter products can delay diagnosis and make later assessment more difficult. A photo on your mobile can be useful for recording a change, but it cannot replace an examination.

When to book urgently

Book a skin check promptly if you have a new spot that is growing, a mole that is changing, or a lesion that bleeds, crusts, itches or will not heal. Seek an earlier appointment if the change is happening over weeks rather than years, or if you have had melanoma before.

If you are unsure whether something counts as a change, act anyway. You do not need to be certain before seeking care. Tell the clinic what you have noticed and when it began. That information can help guide the assessment.

Between appointments, protect your skin with shade, sun-protective clothing, a broad-brimmed hat, sunglasses and broad-spectrum SPF50+ sunscreen used correctly. Prevention matters, but it does not replace checking your skin. The spot you notice today may be nothing serious – and arranging a timely assessment is how you find out.